Do you sink merchants?

[HoofHearted]

Are you supposed to sink the merchant ships when you finish off the actual naval vessels? If so, do you guys waste torps or do you grind out shooting them with the 4" HE gun on the KM subs?

[riggithai]

Yes, submarine warfare was always basically commerce raiding.
Warships were only a bonus and crippling rather than killing was optimal.

Once all the escorts are sunk (or crippled) I surface, pursue and sink the whole convoy. This can take a couple of hours playtime. Only use torps if the target has (nearly) a speed advantage

Good hunting, Kapitan!

[Red Spot]

Subs did not really hunt the combat vessels but preyed upon the merchants trying to cripple the UK's economy and even ability to feed its people.
I.o.w. you could just torp the merchants and remove yourself from the fight.